Sunday, May 30, 2010

Tip of The Month: Block Out That Dirt !

A fellow DomesRO reader asked if there is a "do-it-yourself" method or mod on how to prevent debris, dirt and/or hair from accumulating into the gears of a 500 series Roomba cleaning head module (CHM) and I said YES! The mod comes from the mind of fellow domestic robot fanatic Ed Vickery (a.k.a. "vic7767"). He is a huge contributor at RobotReviews and I have known him for many years from helping out human beings with their sick and tired domestic robots. Keep in mind that these steps created by Ed are for the technically inclined (which is most of us here); for those who do not have the time and/or expertise Ed (a.k.a. "vic7767") can do this mod for a modest service fee. So are you ready to hack your 500 series iRobot Roomba?! Yes? Then just follow these 16 "easy" steps and enjoy!

The Sealed ball bearings used are:

1) 6 x 10 x 3 mm bearing for the brush motor from
2) 10 x 15 x 4 mm bearing for the small rubber brush
3) 15 x 21 x 4 mm bearing for the large brush.

The 15 mm inside diameter ball bearing does not allow much clearance between the square portion of the brush gear and the wall of the ball bearing. If one is concerned you may substitute a larger ID sealed bearing like the 17 x 26 x 5 mm instead but you will have to cut away some of the plastic from the wire brush retainer.

This mod does not cover the actual removal of the CHM from the Roomba. The owners manual and online video at the iRobot site should help the owner with the actual removal of the CHM.






STEP 6: Once the motor is removed it can be turned around and kept in place out of the way using some clear tape.


STEP 8: With plate removed you will be able to access the six gears and the surrounding area to wipe out the lubricant applied during assembly.

STEP 9: Once the six gears are removed they can be cleaned of the lubricant by using liquid soap and a toothbrush.

STEP 10: When filing down the diameter of the brush motor gear a small screw and nut can be used to hold the gear and insert the screw into the end of the drill.

STEP 11: The two larger gears can be inserted into the drill using the metal shaft that is already installed in each. As the diameter is filed down on each gear a test fitting of the ball bearing should be done from time to time so that the bearing has a tight fit.

STEP 12: There are three basic tools that can be used to enlarge the diameter of the holes for the gear assembly. The first tool is a "step drill", the second is a shank mounted grinding stone, and the third is a fine round file.

STEP 13: As each hole is enlarged just enough for a tight fit of the gear with the bearing installed on it, a test fit of the gear next to it can also be done. This helps verify that the gear alignment will be true when all three bearing gears are installed. After all gears are in place the gear cover plate can be trial fitted to make sure the gears are in alignment.

NOTE: The bearing will bind if they are fitted too tight into the hole.

STEP 14: When installing the brush motor check that the motor is in proper alignment with the Green deck and that the deck height adjustment wire is stretched out so the end of it can be reinserted into the slit in the blue cage.

STEP 15: After white lithium grease is applied to the gear teeth surfaces and the metal shafts, install the gear assembly access cover with the six screws. This part will be difficult for most but you might be able to at least test and verify the brush motor and gears will operate without much resistance. Try using a 9 volt battery connected to the red and black leads of the paddle board and verify that the gear assembly will spin. If you can test the amount of current being consumed by the brush motor make sure it is below .5 amps at 16 volts.

STEP 16: Finally install the Green brush assembly back into the blue CHM cage. Make sure the paddle board is in place and the screws tightened so they are flat with the blue plastic case. Make sure the brush deck height adjustment wire is in place and the Red DOT in place or a piece of tape over the plastic slot.

Wow! You reached the end! Hope that this great tip from Ed (a.k.a. "vic7767") has helped you block out the dirt from your Roomba 500 series gear box so it can provide you many years of efficient service.


Anonymous said...

Thank you for posting this! Where can I get the grease you mentioned, as well? That might also be part of the problem, as I had never lubricated it...

Nikolai Tesla said...

Hello Editor SEM,

You are welcomed! I recommend that you use white lithium grease. You can purchase it at your local automotive retailer.

Anonymous said...

Oy, more questions, I'm afraid. *L* We're going to try to do this ourselves, but now that I've followed the link to purchase the bearings, I see there are TONS of options!

The proper bearings are NOT shielded or flanged, correct? I am unable to find the 10x15x4 *sealed* on that page, unless I buy a 10-pack... obviously not my preference. LOL

I found Kit9419 (stainless) and Kit7377 (chrome) for the 6 mm and 15 mm...are those the right ones, at least?

Thanks. :)

Nikolai Tesla said...

Hello Editor SEM,

The correct bearings need to be shielded (for protection) and flanged (for better fit). I would suggest that you purchase just the bearings from Vic if you want to do this project by yourself. You can order just the 3 sealed ball bearing set for $25 including USPS shipping. Just send payment via paypal and make sure to add your mailing address and a comment that you are ordering the bearing set. If this is an international order then each 3 bearing set is $28 shipped.

Paypal =

Hope this helps!

Anonymous said...

Thanks, that will probably be easier. *L* :)

Nikolai Tesla said...

Great to know that you are taking that path. Let us know how your project with the CHM rebuild finished.

Ian said...

I just completed this procedure on my Roomba 560, as dirt in the gearbox has always been a problem for me. I was in the habit of cleaning it out every month. Now, after about a week of cleaning with the bearings installed, there is absolutely NO dirt in the gearbox! This is one of the most useful walk-throughs that I've ever had the pleasure of reading on-line. Thank you for taking time to post this!

Nikolai Tesla said...

Hello Ian,

Sorry for the late response. It is a pleasure to help people like you! Enjoy your efficiently working domestic robot!

Charles said...

I just performed this mod, and wanted to add a couple suggestions on what should be added to the post.
First I think there should be a sentence that warns that if the bearings are too tight, they will bind. I know Ed has warned about this in some forum posts, but I didn't discover those until I had an issue! Secondly, it may be useful to also include the picture he has posted on how the motor installs in.
I was a little in a rush during re-assembly and it this picture would have been nice to have. Otherwise, a great and useful article.

Nikolai Tesla said...

Hello Charles,

Welcome to DomesRO. Thank you for the feedback. I have included a note on Step 13 about bearing binding due to a tight fit in the hole. On step 14 a picture exists on how to mount the motor, I am not sure if you missed it. Hope you continue to visit this site.